part 2 gsm overview

7/31/2019 Part 2 Gsm Overview

1/60

Click to edit Master subtitle style

6/26/12

PART -2

GSM OVERVIEW(DAY 3)


2/60


6/26/12

GSM MobileComm Technologies India

Pvt. Ltd.

Dallas Atlanta W

ashington LA Sao Paulo New Delhi Toronto Muscat Sydney Kenya


3/60

Contents

GSM Overview

GSM Fundamental

Standardized GSM Frequency Bands GSM Architecture and Elements

Interfaces

Identities

Frequency Re Use Concept

BSIC


4/60


6/26/12

Introduction To GSM- 2GFamily

The Global System for Mobile Communications (GSM) is a set ofrecommendations and specifications for a digital cellular telephonenetwork (known as a Public Land Mobile Network, or PLMN).

These recommendations ensure the compatibility of equipment fromdifferent GSM manufacturers, and interconnectivity between differentadministrations, including operation across international boundaries.

GSM networks are digital and can cater for high system capacities.They are consistent with the world-wide digitization of the telephonenetwork, and are an extension of the Integrated Services DigitalNetwork (ISDN), using a digital radio interface between the cellularnetwork and the mobile subscriber equipment.


5/60

GSM-Multiple Access Techniques

GSM Utilizes FDMA/TDMA/FDD techniques

FDMA - Frequency Division Multiple Access

( e.g.: GSM each Frequency channel is 200KHz)

TDMA - Time Division Multiple Access ( e.g.: GSM each frequency channel is divided into 8 timeslots)

FDD Frequency Division Duplex

890-915 MHz (Up Link)

935-960 MHz (Down Link)


6/60

6/26/12

AccessTechnology


7/60

6/26/12

FDMA

UPLINK DOWNLINK

GSM900: 890 MHz - 915 MHz 935 MHz - 960 MHz

GSM1800: 1710 MHz - 1785 MHz 1805 MHz - 1880 MHz

123 ...

Channel 1 -124

1 - 374

200

kHz

123 ...

Duplex frequency 45 MHz / 95MHz

guard band


8/60

TDMAframe

= 8timeslots

=8x.577ms

=4.615ms

01

23

45

7

6

01

23

45

76

01

23

4

5

200

Physicalchannel,

e.g. allocated toone

subscriber withFR voice &no frequency

hopping

frequency

time

TDMAframe

TDMA


9/60

(MHz)

Carrier frequency = ARFCN =Absolute Radio Frequency ChannelNumber

Frequencies are in MHz

GSM systems Uplink Downlink Band

Duplex

Spacing

Duplex

channels

GSM 450

GSM 480

GSM 850

450.4-457.6

478.8-486

824-849

460.4-467.6

488.8-496

869-894

2x7.2

2x7.2

2x25

10

10

45

35

35

124

GSM 900E-GSM (900)R-GSM (900)

890-915880-915876-880

935-960925-960921-925

2x252x352x04

454541

12417440

GSM 1800GSM 1900

1710-17851850-1910

1805-18801930-1990

2x752x60

9580

374299


10/60

GSM Bands

GSM-900 (Channels 125 operating band 900MHz carrier spacing 200 KHzspacing 45MHz)

GSM -1800 (Channels 374 spacing 95MHz)

GSM -1900(Used in USA)

Network Type Frequency Band Uplink/DownlinkGSM900 890-915 / 935-960 MHzGSM1800 1710-1785 / 1805-1880 MHzGSM1900 1850-1910 / 1930-1990 MHz


11/60

Each band is divided into a number of frequency channels, each

having 200 KHz bandwidth. Therefore 124 channels available for each UL and DL in GSM 900 and

374 channels available in GSM 1800.

GSM 900 = 1 TO 124

GSM 1800= 512 TO 885

To calculate actual frequency:

For GSM 900 Band

UL freq- Fu(n)=890+0.2n (1


12/60

Frequency division multiple Access

Uplink 890 MHz to 915 MHzDown Link 935 MHz to 960 MHz25 MHz divided into 125 channels of 200 KHz bandwidth

890.0 890.2 890.4 914.8 915.0

935.0 935.2 935.4 959.8 960.0

UL

D

L

Access Techniques


13/60

Time Division Multiple Access

Each carrier frequency subdivided in time domain into 8 timeslotsEach mobile transmits data in a frequency, in its particulartime slot - Burst period = 0.577 millisecond (ms).8 time slots called a TDMA frame. Period is 0.577 * 8 = 4.615ms

0 1 2 3 4 5 6 7

4.615 ms

0.577 ms

Access Techniques


14/60

GSM Time Division MultiplexFrame and Physical Channels

TS TS TS TS TS TS TSTS

0 1 2 3 4 5 6 7

Time

4.615ms

TDMAframe

Physical channel # 2 = recurrence oftime-slot # 2

TDMAframe

0 9.23ms

Time-slot

(frames repeat continuously)

T S TS TS TS TS TS TS TS

0 1 2 3 4 5 6 7

TDMA Frames

L i


15/60

Why uplink band consists of lower range of frequencies?

Logic

It is because higherfrequency has higherthe channelattenuation, and BTShas more transmittingpower capability tocompensate thoselosses as compare toMS.


16/60


6/26/12

GSM Architecture Overview

e wor


17/60

AuC

MS

MS

BTS

BTS

BTS

BSC

BSC

MSS/MGW

MSS/MGW

VLR

VLR

GMSC

HLR

PSTN

EIR

Um

Abis

Abis A

A

OMC

Server

Um

- e worStructure

B

E

E

X.25

C

F

H

X.25

M bil St ti


18/60

Mobile Station

The Mobile Station (MS) consists of the physical equipment used by a

PLMN subscriber to connect to the network. It comprises the Mobile Equipment (ME) and the Subscriber Identity

Module (SIM).

The ME forms part of the Mobile Termination (MT) which, depending onthe application and services, may also include various types of Terminal

Equipment (TE) and associated Terminal Adapter (TA).

M bil St ti


19/60

6/26/12

Mobile Station

Important Terms


20/60

Important Terms

IMEI International Mobile Equipment Identifier.

The IMEI is an internationally-unique serial number allocated to the MShardware at the time of manufacture. It is registered by the networkoperator and (optionally) stored in the AuC for validation purposes.

IMEI = TAC + FAC + SNR +sp

TAC = Type Approval Code by central GSM body

FAC = Final Assembly Code, identifies the manufacturerSNR = Serial Number, unique six digit number

sp = spare for future use

*#06# is the digits to find out the serial number of MS

Important Terms


21/60

IMSI International Mobile Subscriber Identifier

When a subscriber registers with a network operator, a unique subscriber

IMSI identifier is issued and stored in the SIM of the MS as well as in the

HLR . An MS can only function fully if it is operated with a valid SIM

inserted into an MS with a valid IMEI. IMSI consist of three parts:

MCC MNC MSIN

Max. 15 digits

MCC Mobile Country Code.MNC Mobile Network Code.

MSIN Mobile Subscriber Identification Number.

Important Terms

Important Terms


22/60

TMSI Temporary Mobile Subscriber Identity

A TMSI is used to protect the true identity (IMSI) of a subscriber. It is issued

by and stored within a VLR (not in the HLR) when an IMSI attach takes

place or a Location Area (LA) update takes place. At the MS it is stored in

the MSs SIM. The issued TMSI only has validity within a specific LA.

Since TMSI has local significance, the structure may be chosen by theadministration. It should not be more than four octets.

Important Terms

Important Terms


23/60

MSISDN Mobile Station ISDN Number

The MSISDN represents the true or dialled number associatedwith the subscriber. It is assigned to the subscriber by the networkoperator at registration and is stored in the SIM.

MSISDN Mobile Subscriber ISDN number

Subscriber Related Identities -

CC NDC SN

Max. 15 digits

CC Country Code.NDC Network Destination Code.SN Subscriber Number.

E.g. - 98100-12345

Important Terms

Important Terms


24/60

MSRN Mobile Station Roaming Number

The MSRN is a temporary, location-dependant ISDN numberissued by the parent VLR to all MSs within its area ofresponsibility. It is stored in the VLR and associated HLR but notin the MS. The MSRN is used by the VLR associated MSC for callrouting within the MSC/VLR service area.

Format : MSRN = CC + NDC + SN

CC = Country Code

NDC = Network Destination Code

SN = Subscriber Number

Important Terms

MSRN


25/60

6/26/12

PSTN GMSC

HLR

MSCVLR

MSISDN

1

MSISDN2

IMSI

3

IMSI MSRN4

MSRN

5

MSRN 6

MSRN

7

MSRN

Gateway MSC (GMSC)


26/60

Gateway MSC (GMSC)

MS


27/60

The IMSI identifies the subscriber within the GSM network while theMS ISDN is the actual telephone number a caller (possibly in another

network) uses to reach that person.

Security is provided by the use of an authentication key and by thetransmission of a temporary subscriber identity (TMSI) across theradio interface where possible to avoid using the permanent IMSI

identity.

The IMEI may be used to block certain types of equipment fromaccessing the network if they are unsuitable and also to check forstolen equipment.

MSIdentities

Mobile


28/60

The Mobile Station consists of :

Mobile Equipment (ME)

Subscriber Identity Module (SIM)

The SIM stores permanent and temporary data about the mobile, thesubscriber and the network, including :

The International Mobile Subscribers Identity (IMSI)

MS ISDN number of subscriber

Authentication key (Ki) and algorithms for authentication check

The mobile equipment has a unique International Mobile EquipmentIdentity (IMEI), which is used by the EIR

MobileStation

Mobile


29/60

6/26/12

MobileStation

Mobile Station


30/60

6/26/12

Mobile StationFunctionality

BSS


31/60

Base Station Subsystem (BSS)

BSS

BS


32/60

The BSS comprises:

Base Station Controller (BSC) Base Transceiver Stations (BTSs)

Transcoder and rate adaptation unit (TRAU)

The purpose of the BTS is to:

provide radio access to the mobile stations manage the radio access aspects of the system

BTS contains:

Radio Transmitter/Receiver (TRX)

Signal processing and control equipment

Antennas and feeder cables

BSS

Base Transceiver Station (BTS)


33/60

6/26/12

Base Transceiver Station (BTS)

Air interface signalling

Ciphering

Speech processing (channel coding, interleaving, and burst formatting)

Generation of alarms and statistics

Base band/Radio frequency transformation

BS


34/60

The BSC:

allocates a channel for the duration of a call maintains the call:

monitors quality

controls the power transmitted by the BTS or MS

generates a handover to another cell when required

BSC


35/60

Co-located BTS: BTS is situated along with BSC or the

MSC and no additional E1 link is required.

BSC

BTS

Remote BTS : BTS is situated in a stand alone position andadditional E1links are required to connect to BSC.

BSC

BTS

BSS Configuration1/3


36/60

Daisy Chain

Star Configuration

Loop

Configuration


BSS Configuration


37/60

Comparison of DifferentConfigurations

Daisy Chain: Easy to implement, effective utilization of transmissionlinks but if one of the link fails, all the BTSs connected in the chain willwent off.

Star Configuration: Easy to implement but poor utilization of links. Each

BTS require one E1 to connect to BSC. But if link goes down onlyindividual BTS will be affected.

Loop Configuration: Slightly difficult to implement but effectiveutilization of E1 links. Even if one link goes off BTS will continue tocommunicate with the network from the other side.


i (TRAU)


38/60

nit (TRAU)

The primary function of the TRAU is to convert 16kps (inc signaling)

GSM speech channels to 64kbps.

The reason this process is necessary is because MSCs only switch atthe 64kbps channel level.

TCTranscoding

BlaBlaBlaBlaBlaBla

Conversion of Speech Data (CNRAN): CN: 64 kbit/s RAN: 4.75 13 kbps Depending uponcodec

Speech andSignaling

16Kbps

64kbit/s

RAN

CN


39/60


6/26/12

NSS Elements

Introducti


40/60

Introduction

Network Sub System can be considered as a heart of the GSM

Network. All the major activities like switching of calls, routing, securityfunctions, call handling, charging, operation & maintenance, handoverdecisions, takes place within the entities of NSS.

Various kinds of interfaces are used to communicate between the

different entities. Different methods are used to optimize and providethe quality network with the minimum operating cost.


41/60

Network Switching System(NSS)

The NSS combines the call routing switches (MSCs and GMSC) withdatabase registers required to keep track of subscribers movementsand use of the system.

Call routing between MSCs is taken via existing PSTN or ISDNnetworks. Signaling between the registers uses Signaling System No. 7

protocol.

NSS

Network Switching System


42/60

Network Switching System(NSS)

Key elements of the NSS:

Mobile Switching Server (MSS)

Media Gateway (MGW)

Visitor Location Register (VLR)

Home Location Register (HLR)

Authentication Center (AuC)

Equipment Identity Register (EIR)

Gateway MSC (GMSC)

These elements are interconnected by means of an SS7 network


43/60

GSM Architecture

Main MSS functions: Switching Call Setup Call Ticketing Interfaces

Main MGW functions: Adapt signaling (control plane) Connect the user data (user plane) Provide tones and announcements to end users.

Perform the transcoding and signal processing for the userplane when needed.

Mobile Switching Server (MSS)


44/60

g ( )

Main MGW functions: Adapt signaling (control plane) Connect the user data (user plane) Provide tones and announcements to end users. Perform the transcoding and signal processing for the user plane when needed.

Main MSS functions: Switching Call Setup Call Ticketing Interfaces

MS


45/60

The following are typical MSS functions in a cellular system:

Provide switched connections with PSTN

Provide switched connections between mobile subscribers

Provide coordination over signaling with mobiles

Coordinate the location and handover process

Provide custom services to mobile users

Collect billing data

Switching calls, controlling calls and logging calls

Interface with PSTN, ISDN, PSPDN

Mobility management over the radio network and other networks

Radio Resource management - handovers between BSCs

Billing Information

S

VLR is responsible for


46/60

6/26/12

p

Setting up and controlling calls along with supplementary services.

Continuity of speech (Handover)

Location updating and registration

Updating the mobile subscriber data.

Maintain the security of the subscriber by allocating TMSI

Receiving and delivering short messages

Handling signaling to and from- BSC and MSs

- other networks e.g. PSTN, ISDN

IMEI check

Retrieve data from HLR like authentication data, IMSI,ciphering key

VLR


47/60

Retrieve information for incoming calls.

Retrieve information for outgoing calls.

Attach/Detach IMSI

Search for mobile subscriber, paging and complete the call.


48/60

Home Location Register

HLR is a database that stores subscription and set of functionsneeded to manage subscriber data in one PLMN area. Any

administrative action by the service provider or changes made bysubscriber is first carried out on the HLR and then update the VLR.

Beside the permanent data it also include dynamic data of homesubscriber including VLR address, call forward number and callbarring numbers.

Triplets are also stored in the HLR for the authentication purpose.

(EIR)


49/60

(EIR)

Purpose of this feature is to make sure that no stolen or unauthorizedmobile equipment is used in the network.

EIR is a database that stores a unique International Mobile EquipmentIdentity (IMEI) number for each item of mobile equipment.

Storing IMEIs(counterpart: ME)on White / Gray / BlackList Performing IMEI Checkon VLR / SGSN request

optional network function

IMEIInternationa

lMobilestation

EquipmentIdentity

Authentication Center (AUC)


50/60

AUC is always integrated with HLR for the purpose of the

authentication. At subscription time, the Subscriber AuthenticationKey (Ki) is allocated to the subscriber, together with the IMSI. TheKi is stored in the AUC and used to provide the triplets, same Ki isalso stored in the SIM.

AUC stores the following information for each subscriber

1. The IMSI number,

2. The individual authentication key Ki,

3. A version of A3 and A8 algorithm.

Billing Center


51/60

For Post Paid Subscribers: Charging analysis is the process ofanalyzing the Charging Case and then ultimately generating the TT (TollTicketing) record so that an itemized bill can be produced and then senton to the customer.

For Prepaid Subscribers: Intelligent Network (IN) is used for Billing

Gateway MSC (GMSC)


52/60

Gateway MSC (GMSC) connects the PLMN with other networks and

the entry point for the mobile subscriber calls having theinterrogation facility.

It has the function to obtain the information from the HLR about thesubscribers current location and reroute the calls accordingly.

In case of the network having only one MSC, the same MSC workas the GMSC, while in the case having more than one MSC, onededicated MSC works as GMSC.

SMS Applications


53/60

SMS up to 160 alphanumeric characters.

Alert services (MT-SMS)

Voice Message Alert

FAX/Telex Message Alert

E-mail System Alert

Information Services

Financial Services (stock market queries and alerts)

Weather or traffic information (e.g., from TV/radio station datafeeds)

A-Interface (MSC BSC)


54/60

( )

The interface between the MSC and its BSS is specified in the 08-series of

GSM Technical Specifications. The BSS-MSC interface is used to carryinformation concerning:

BSS Management;

Call handling;

Mobility Management.

Interfa


55/60

6/26/12

BSC

TCBTS

BT

S

V

L

R

(G)MSC

E

I

R

H

L

R

A

C

Um

AAter

Abis

B C

D

V

L

R

G

F

E

BSS

NSS

BSC

TCBTS

BT

S (MSS/MGW)

Um

AAter

Abis

B C

D

VLR

EIR

HLR

AC

VL

R

G

F

GMS

E

BSS

NSS

ces


56/60


6/26/12

OSS Functionality

Operation And Maintenance Center


57/60

Operation And Maintenance Center(OMC)

The OMC centralizes all operations and maintenance activities for theMSCs and BSSs using remote software control.

It provides remote testing, operations, and maintenance capabilitiesfor the entire system from one central location.

Each BSS, MSC, HLR, VLR, EIR, and AUC can be monitored andcontrolled from the OMC.

It is termed as NOC (Network Operation Centre) also

OMC F ti l A hit t


58/60

OMC Functional Architecture

OperatingSystem

Communications

Handler

Database

MMI

Event/ AlarmManagement

SecurityManagement

FaultManagement

PerformanceManagement

ConfigurationManagement

Alarms


59/60

Types of Alarm:

1) Internal : Major and Minor

2) External : Major and Minor

Major : Need to be escalated and require solution immediately. Lessdelay

Minor: It is important and escalated, but can afford some delay

Alarms

OSS


60/60

X.25 Interfaces

The diagram shows the X.25 packet data connections of thesystem.

The X.25 packets provide the OMC with communications to allthe entities over which it has control and oversight. Remember thatthese X.25 connections will commonly be contained within 2 Mbit/s

links using a dedicated timeslot.

Note that the X.25 connection from the OMC to the BSS may benailed through (or permanently connected by software) at theMSC, or may be supported by a completely independent physicalroute.

OSSInterface

part 2 gsm overview

Documents